The amount of a phosphatidylethanolamine O-18:2_18:2 when measured in blood serum. The trait is level of Phosphatidylethanolamine (O-18:2_18:2) in blood serum (OBA_2045150, an Ontology of Biological Attributes identifier). Also known as: blood serum phosphatidylethanolamine O-18:2_18:2 amount, level of phosphatidylethanolamine O-18:2_18:2 in blood serum.